The helicase Has1p is required for snoRNA release from pre-rRNA
The helicase Has1p is required for snoRNA release from pre-rRNA
复制标题
DOI：
10.1128/mcb.00664-06
复制
发表时间：
2006-10-01
影响因子：
5.3
通讯作者：
Fournier, Maurille J.
中科院分区：
文献类型：
--
作者：
Liang, Xue-hai;Fournier, Maurille J.
真核生物中 rRNA 的合成涉及大量 snoRNA-蛋白质复合物 (snoRNP) 的作用，这些复合物产生修饰的核苷酸并参与前 rRNA 的切割。 snoRNP 通过直接碱基配对（在许多情况下通过长互补序列）介导这些功能。这一特征表明 RNA 解旋酶可能参与前 rRNA 中 snoRNP 的结合和释放。在这项研究中，我们确定 DEAD 盒解旋酶 Has1p（一种产生 18S rRNA 所需的核仁蛋白）与处理 snoRNP 的 snR30/U17 共纯化，但也与其他 snoRNP 一起存在。阻断 Has1p 表达会导致与 60S-90S 核糖体前 RNP 复合物相关的 snoRNP 大幅增加，包括处理 snoRNP 的 U3 和 U14 以及检查的几种修饰 snoRNP。即使在脱蛋白后，共沉降仍持续存在。当两种非解旋酶蛋白 Esf1p 和 Dim2p 耗尽时，没有观察到这种效应，这两种蛋白也是 18S rRNA 产生所必需的。 HasIp 的 ATP 酶和解旋酶基序的点突变阻止 U14 从 pre-rRNA 中释放。令人惊讶的是，HasIp 的消耗导致游离 U6 snRNP 水平降低。结果表明 Has1p 解旋酶是 snoRNA 从 pre-rRNA 释放和 U6 snRNP 产生所必需的。
Synthesis of rRNA in eukaryotes involves the action of a large population of snoRNA-protein complexes (snoRNPs), which create modified nucleotides and participate in cleavage of pre-rRNA. The snoRNPs mediate these functions through direct base pairing, in many cases through long complementary sequences. This feature suggests that RNA helicases may be involved in the binding and release of snoRNPs from pre-rRNA. In this study, we determined that the DEAD box helicase Has1p, a nucleolar protein required for the production of 18S rRNA, copurifies with the snR30/U17 processing snoRNP but is also present with other snoRNPs. Blocking Has1p expression causes a substantial increase in snoRNPs associated with 60S-90S preribosomal RNP complexes, including the U3 and U14 processing snoRNPs and several modifying snoRNPs examined. Cosedimentation persisted even after deproteinization. This effect was not observed with depletion of two nonhelicase proteins, Esf1p and Dim2p, that are also required for 18S rRNA production. Point mutations in ATPase and helicase motifs of HasIp block U14 release from pre-rRNA. Surprisingly, depletion of HasIp causes a reduction in the level of free U6 snRNP. The results indicate that the Has1p helicase is required for snoRNA release from pre-rRNA and production of the U6 snRNP.